From nobody Mon Feb 9 12:25:20 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 15FF7C6FD1D for ; Thu, 23 Mar 2023 04:01:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230353AbjCWEBP (ORCPT ); Thu, 23 Mar 2023 00:01:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37610 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229889AbjCWEAx (ORCPT ); Thu, 23 Mar 2023 00:00:53 -0400 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 915CC2005E for ; Wed, 22 Mar 2023 21:00:49 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id e129-20020a251e87000000b00b56598237f5so21501786ybe.16 for ; Wed, 22 Mar 2023 21:00:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1679544049; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=xrG0SezuE3D1BzHk1bOIN+tOwhU+wFsyLck18RLDkiM=; b=cgw7YjSYw+yZCrYg4MWNWyL1ocWVlMfhI6U/IH5SNNI/KXZEirBQTnVHw1Jk19ca7x YZMRDXY2GIXRShVJyUBfGcwrm5OQ54Bn3XOEBif3BbHD9ArewU0b2vLyFm38bp8+NRx8 4lwk3DHRAIpY5JhlVhZi+qJFnS5DTPOFtneU65+9wwMhEPN3ScjeohcSLADEGreopxgz hPSmYPd9gVS979yLkwNh9j+9QGCIU5M1yATespEadqsIAym+pG18x2O6VFUlYJCK8ejc v8yJF8c/6m0MiyUkNdlDzwM4KjC9ikuULQ0wGXuneSrTmETcMqRGnUz3Mhll67JgWKef njxw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1679544049; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=xrG0SezuE3D1BzHk1bOIN+tOwhU+wFsyLck18RLDkiM=; b=MR1O9Qxzk6nZixuEj25uHXaHsvr9cgOjAGZFSylwaaoUVWKDd6T4/1zSBu9oGWpZSz wGxg+NcT8hB2yCtU7QPQOcPdyM2n0fsIkG+H5PW/DfmkR6iQI95R19yu0KVCMdNPFCUz BHuQa6AawxQM6Urs2nsvpzhsOk6K4sqZxsy/0UuboIZmXqCaOto//bEnIVTWzAq5nkTD Opb8ecbyeLRdKzPGjPoOmLvf0MGGmtVNWj51lNkKgIyrWKUAMjcfvwX5nJ1w7BJjcBV2 HOv1G0rxc+MsUg/z/1xED3QTNMfRWfcIn5p531E2pQkX11KjEBNk6J56wvSzNAJgEgsR pbdg== X-Gm-Message-State: AAQBX9d0+OlOfmDdEvmoGvWT/FEM6qAFARYNj2wI9ehZYUZ6eE0vgM6R /xJfwHf4TiuicN3HBTqGX2o0yTMYJVaaBUlM X-Google-Smtp-Source: AKy350bTQGWCAJk1730fCXLD+nAem5ueAaNE2q7H+XY1RCF27byWvmJXxhgyQR2PhcI0/Laslob9u/xZD8mfS05D X-Received: from yosry.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:2327]) (user=yosryahmed job=sendgmr) by 2002:a81:b149:0:b0:544:bb1e:f9cf with SMTP id p70-20020a81b149000000b00544bb1ef9cfmr1185027ywh.4.1679544048914; Wed, 22 Mar 2023 21:00:48 -0700 (PDT) Date: Thu, 23 Mar 2023 04:00:34 +0000 In-Reply-To: <20230323040037.2389095-1-yosryahmed@google.com> Mime-Version: 1.0 References: <20230323040037.2389095-1-yosryahmed@google.com> X-Mailer: git-send-email 2.40.0.rc1.284.g88254d51c5-goog Message-ID: <20230323040037.2389095-5-yosryahmed@google.com> Subject: [RFC PATCH 4/7] memcg: sleep during flushing stats in safe contexts From: Yosry Ahmed To: Tejun Heo , Josef Bacik , Jens Axboe , Zefan Li , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton Cc: Vasily Averin , cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, Yosry Ahmed Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Currently, all contexts that flush memcg stats do so with sleeping not allowed. Some of these contexts are perfectly safe to sleep in, such as reading cgroup files from userspace or the background periodic flusher. Enable choosing whether sleeping is allowed or not when flushing memcg stats, and allow sleeping in safe contexts to avoid unnecessarily performing a lot of work without sleeping. Signed-off-by: Yosry Ahmed --- include/linux/memcontrol.h | 8 ++++---- mm/memcontrol.c | 35 ++++++++++++++++++++++------------- mm/vmscan.c | 2 +- mm/workingset.c | 3 ++- 4 files changed, 29 insertions(+), 19 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index b6eda2ab205d..0c7b286f2caf 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1036,8 +1036,8 @@ static inline unsigned long lruvec_page_state_local(s= truct lruvec *lruvec, return x; } =20 -void mem_cgroup_flush_stats(void); -void mem_cgroup_flush_stats_delayed(void); +void mem_cgroup_flush_stats(bool may_sleep); +void mem_cgroup_flush_stats_delayed(bool may_sleep); =20 void __mod_memcg_lruvec_state(struct lruvec *lruvec, enum node_stat_item i= dx, int val); @@ -1531,11 +1531,11 @@ static inline unsigned long lruvec_page_state_local= (struct lruvec *lruvec, return node_page_state(lruvec_pgdat(lruvec), idx); } =20 -static inline void mem_cgroup_flush_stats(void) +static inline void mem_cgroup_flush_stats(bool may_sleep) { } =20 -static inline void mem_cgroup_flush_stats_delayed(void) +static inline void mem_cgroup_flush_stats_delayed(bool may_sleep) { } =20 diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 72cd44f88d97..39a9c7a978ae 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -634,7 +634,7 @@ static inline void memcg_rstat_updated(struct mem_cgrou= p *memcg, int val) } } =20 -static void __mem_cgroup_flush_stats(void) +static void __mem_cgroup_flush_stats(bool may_sleep) { /* * This lock can be acquired from interrupt context, but we only acquire @@ -644,26 +644,26 @@ static void __mem_cgroup_flush_stats(void) return; =20 flush_next_time =3D jiffies_64 + 2*FLUSH_TIME; - cgroup_rstat_flush(root_mem_cgroup->css.cgroup, false); + cgroup_rstat_flush(root_mem_cgroup->css.cgroup, may_sleep); atomic_set(&stats_flush_threshold, 0); spin_unlock(&stats_flush_lock); } =20 -void mem_cgroup_flush_stats(void) +void mem_cgroup_flush_stats(bool may_sleep) { if (atomic_read(&stats_flush_threshold) > num_online_cpus()) - __mem_cgroup_flush_stats(); + __mem_cgroup_flush_stats(may_sleep); } =20 -void mem_cgroup_flush_stats_delayed(void) +void mem_cgroup_flush_stats_delayed(bool may_sleep) { if (time_after64(jiffies_64, flush_next_time)) - mem_cgroup_flush_stats(); + mem_cgroup_flush_stats(may_sleep); } =20 static void flush_memcg_stats_dwork(struct work_struct *w) { - __mem_cgroup_flush_stats(); + __mem_cgroup_flush_stats(true); queue_delayed_work(system_unbound_wq, &stats_flush_dwork, FLUSH_TIME); } =20 @@ -1570,7 +1570,7 @@ static void memory_stat_format(struct mem_cgroup *mem= cg, char *buf, int bufsize) * * Current memory state: */ - mem_cgroup_flush_stats(); + mem_cgroup_flush_stats(true); =20 for (i =3D 0; i < ARRAY_SIZE(memory_stats); i++) { u64 size; @@ -3671,7 +3671,11 @@ static unsigned long mem_cgroup_usage(struct mem_cgr= oup *memcg, bool swap) unsigned long val; =20 if (mem_cgroup_is_root(memcg)) { - mem_cgroup_flush_stats(); + /* + * mem_cgroup_threshold() calls here from irqsafe context. + * Don't sleep. + */ + mem_cgroup_flush_stats(false); val =3D memcg_page_state(memcg, NR_FILE_PAGES) + memcg_page_state(memcg, NR_ANON_MAPPED); if (swap) @@ -4014,7 +4018,7 @@ static int memcg_numa_stat_show(struct seq_file *m, v= oid *v) int nid; struct mem_cgroup *memcg =3D mem_cgroup_from_seq(m); =20 - mem_cgroup_flush_stats(); + mem_cgroup_flush_stats(true); =20 for (stat =3D stats; stat < stats + ARRAY_SIZE(stats); stat++) { seq_printf(m, "%s=3D%lu", stat->name, @@ -4090,7 +4094,7 @@ static int memcg_stat_show(struct seq_file *m, void *= v) =20 BUILD_BUG_ON(ARRAY_SIZE(memcg1_stat_names) !=3D ARRAY_SIZE(memcg1_stats)); =20 - mem_cgroup_flush_stats(); + mem_cgroup_flush_stats(true); =20 for (i =3D 0; i < ARRAY_SIZE(memcg1_stats); i++) { unsigned long nr; @@ -4594,7 +4598,12 @@ void mem_cgroup_wb_stats(struct bdi_writeback *wb, u= nsigned long *pfilepages, struct mem_cgroup *memcg =3D mem_cgroup_from_css(wb->memcg_css); struct mem_cgroup *parent; =20 - mem_cgroup_flush_stats(); + /* + * wb_writeback() takes a spinlock and calls + * wb_over_bg_thresh()->mem_cgroup_wb_stats(). + * Do not sleep. + */ + mem_cgroup_flush_stats(false); =20 *pdirty =3D memcg_page_state(memcg, NR_FILE_DIRTY); *pwriteback =3D memcg_page_state(memcg, NR_WRITEBACK); @@ -6596,7 +6605,7 @@ static int memory_numa_stat_show(struct seq_file *m, = void *v) int i; struct mem_cgroup *memcg =3D mem_cgroup_from_seq(m); =20 - mem_cgroup_flush_stats(); + mem_cgroup_flush_stats(true); =20 for (i =3D 0; i < ARRAY_SIZE(memory_stats); i++) { int nid; diff --git a/mm/vmscan.c b/mm/vmscan.c index 9c1c5e8b24b8..59d1830d08ac 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2845,7 +2845,7 @@ static void prepare_scan_count(pg_data_t *pgdat, stru= ct scan_control *sc) * Flush the memory cgroup stats, so that we read accurate per-memcg * lruvec stats for heuristics. */ - mem_cgroup_flush_stats(); + mem_cgroup_flush_stats(false); =20 /* * Determine the scan balance between anon and file LRUs. diff --git a/mm/workingset.c b/mm/workingset.c index 00c6f4d9d9be..042eabbb43f6 100644 --- a/mm/workingset.c +++ b/mm/workingset.c @@ -462,7 +462,8 @@ void workingset_refault(struct folio *folio, void *shad= ow) =20 mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + file, nr); =20 - mem_cgroup_flush_stats_delayed(); + /* Do not sleep with RCU lock held */ + mem_cgroup_flush_stats_delayed(false); /* * Compare the distance to the existing workingset size. We * don't activate pages that couldn't stay resident even if --=20 2.40.0.rc1.284.g88254d51c5-goog